Some existing diesel railcar drive systems are formed as a system for entering the output of a diesel engine to a transmission, and transmitting the output of the transmission via a drive shaft to wheels. According to such a system, every gear shift is performed via the transmission. On the other hand, a different type of drive system has been proposed, wherein all the output of the engine is entered to the generator, and the electric energy output from the generator is entered to the inverter and subjected to frequency conversion so as to electrically drive motors mounted on a bogie. Even if the engine has stopped, power obtained from a battery can drive the motors. According to this type of drive system, during deceleration regeneration, either full power or excessive power according to the drive state of the car is charged to the battery.
There has been disclosed a bridge-type transmission having two intermediate shafts, wherein a backward gear is disposed between the input shaft and the intermediate shaft (refer to patent document 1). The transmission is an active shift transmission including first and second intermediate shafts disposed between a transmission input shaft connected to the engine and a transmission output shaft, and speed change gears disposed between the intermediate shaft and the input shaft and between the intermediate shaft and the output shaft, wherein the transmission ratio is determined by the two sets of speed change gear ratios, and in addition, a differential device is connected between the intermediate shafts, an electric motor is connected to a third shaft of the differential device, and active variable speed is performed by making a motor temporarily carry the engine torque. If the speed change gear of the input shaft is released without increasing the number of engagement clutches, and the drag loss of engine at the time of regenerative braking can be prevented by detaching the engine. However, since the present active shift transmission is for automobiles, there is only one (single side) backward gear.
Further, an automatic transmission formed by inserting an electric motor between both clutch shafts of a twin clutch type automatic transmission is proposed to control the torque and rotation speed of the electric motor for smooth and efficient speed change control and to realize creep control, idle stop start control, and R→D/D←R select control (refer to patent document 2). The proposal includes automatic transmission having a fixed brake or a fixing clutch disposed on one of the intermediate shafts, but the object thereof is restricted to starting the engine.
Patent document 1: Japanese patent application laid-open publication No. 2005-76875
Patent document 2: WO01/66971